98 GC8 JDM Boost Issues

[SimJen]

Guys,

I'm after a few suggestions from you knowledgeable bunch of Sub experts

I've got a 98 GC8 JDM

Its running a STI TMIC, MRT Water Spray system and has been running well at 16 PSI or so all day long. Stock BOV and solenoids etc, Walbro pump, grunty uppipe and muffler system.

Runs clean and doesn't smoke at all.

Always runs on BP Ultimate no question.

2 days ago I put $40 of BP Ultimate in and it started running weird. Boost won't go over 0.5-0.7 bar and it splutters as it gets there, either feels like a boost/fuel cut or the timing being retarded!

I thought it might be bad fuel so I went and put another $40 of 98 from a different pump but at the same servo (Cambridge BP) as I can't get 98 anywhere else locally.

I still don't know if its bad fuel?? but am guessing it might be something else.

Anyway I've tried pulling the boost solenoid and cleaning it and it seems to be working, pulled various hoses and blown them out. Restrictor pill is still installed.

Tried running as a test without the wastegate hoses on to see if it was running with wastegate pressure limits but still wouldn't boost above 0.7 or so cleanly, just seems to stumble?

Is this something that the AFM would cause? or a faulty 02?

I've yet to pull the rest of the hoses off to check for leaks under the intercooler, when I fitted the STI TMIC I put all new Silicones on, and that was 6 months ago!!

It has always been a little hesitant to start sometimes (maybe 4-5 cranks?) but it still starts! Could this be a precurser to my problem?

My black read plugs under the dash seem to have a couple of wires pulled from them so I can't read any CEL's unless someone can tell me what the colours should be?

Any ideas? I'd appreciate some input.

[zarnah]

 SimJen said:

Guys,

I'm after a few suggestions from you knowledgeable bunch of Sub experts

I've got a 98 GC8 JDM

Its running a STI TMIC, MRT Water Spray system and has been running well at 16 PSI or so all day long. Stock BOV and solenoids etc, Walbro pump, grunty uppipe and muffler system.

Runs clean and doesn't smoke at all.

Always runs on BP Ultimate no question.

2 days ago I put $40 of BP Ultimate in and it started running weird. Boost won't go over 0.5-0.7 bar and it splutters as it gets there, either feels like a boost/fuel cut or the timing being retarded!

I thought it might be bad fuel so I went and put another $40 of 98 from a different pump but at the same servo (Cambridge BP) as I can't get 98 anywhere else locally.

I still don't know if its bad fuel?? but am guessing it might be something else.

Anyway I've tried pulling the boost solenoid and cleaning it and it seems to be working, pulled various hoses and blown them out. Restrictor pill is still installed.

Tried running as a test without the wastegate hoses on to see if it was running with wastegate pressure limits but still wouldn't boost above 0.7 or so cleanly, just seems to stumble?

Is this something that the AFM would cause? or a faulty 02?

I've yet to pull the rest of the hoses off to check for leaks under the intercooler, when I fitted the STI TMIC I put all new Silicones on, and that was 6 months ago!!

It has always been a little hesitant to start sometimes (maybe 4-5 cranks?) but it still starts! Could this be a precurser to my problem?

My black read plugs under the dash seem to have a couple of wires pulled from them so I can't read any CEL's unless someone can tell me what the colours should be?

Any ideas? I'd appreciate some input.

sounds like your ecu has picked up on something and gone into limp mode, try re-setting the ecu and see if it sorts its shit out

[funkytown]

id suggest an afm and in limp mode

[SimJen]

I left my circuit breaker off last night so the ecu would have reset, still the same on my morning commute to work?

Might give the AFM a bit of clean tonight see if that fixes anything!

[Ninja8)]

Purchase a can of CRC AFM cleaner..worked its magic on me and a mates afm.

[SimJen]

I did clean it about 6 months ago, but only because I was doing other things. I hope its not farked, worst time of year to get a new one!!

[Ninja8)]

CRC afm cleaner might do you the trick...i guess $25 is better than $150 (2nd hand) or $400 (Brand New)

[SimJen]

Well I've fixed it!

Simple issue, took out the AFM and gave it a clean. Upon putting it back in I noticed the rear drivers side sparkplug lead in the head was sticking out slightly further than the front one. Seems the plug lead is quite loose on the spark plug and as such had come away just enough to cause a misfire at 4-5000rpm which also seemed to cause the boost to be dropped!

Pushed it on and went for a blast and bammo, its all back to normal!!

About time I had some luck!

Cheers for the help though guys

Si

[Pappu1]

good to see u got it sorted bro...nice detective work

[Guest S T E Y E]

haha daym that was a easy fix i wish they were all like that hahaha